Altitude Response of Thermosphere Mass Density to Geomagnetic Activity in the

Recent Solar Minimum

Jeffrey P. Thayer, Xianjing Lui, and Jiuhou Lei

MURI NADIR Meeting 25–26 October 2011

A Compressed Thermosphere Leads to a Greater % Change in Density Response Given the Same Energy Input – Preconditioning by EUV Flux

Relative changes in thermosphere density response to geomagnetic forcing is stronger under low EUV conditions

0 0

0 11

0 1 0 0 1

( , ) ( , )( , ) exp( , ) ( , ) ( , ) ( ) ( )

h h

h h

T t h m t ht h dh dht h T t h m t h H t H t

Absolute Density at 400 km

Relative Perturbations

Quiet

A

Active

B

C

P2

P1

Satellite altitudeAlti

tude

h

1 1( ), ( )T t m t0 0( ), ( )T t m t

ah

qh

lnZ d P

In 2008, the Solar EUV Flux was at an Extreme Minimum with Little Change over the Year While 38 CIRS were Catalogued!!

Density - 400km altitude

Solar wind density

IMF Bx

Geomagnetic Activity Index

Solar wind speed

IMF Bz

IMF |B|

Classical CIR

The interplanetary conditions for different types of geomagnetic activity are indicated by numbers: (1) geomagnetic quiet, (2) a storm initial phase, (3) a magnetic storm main phase, and (4) thestorm extended ‘‘recovery’’ phase.

Tsurutani, B. T., et al. (2006), Corotating solar wind streams and recurrent geomagnetic activity: A review, J. Geophys. Res., 111, A07S01, doi:10.1029/2005JA011273.

Superposed Epoch Analysis of 29 CIR/HSS in 2008

Thermospheric response to CIRs globally

Calm

Lei, J., J. P. Thayer, W. Wang, and R. L. McPherron (2011), Impact of CIR storms on thermosphere density variability during the solar minimum of 2008, Sol. Phys., doi:10.1007/s11207-010-9563-y.

Superposed-Epoch Analysis of CHAMP Thermosphere Density in 2008

Altitude Response of Mass Density using CHAMP and GRACE Measurements

CHAMP Satellite – GFZ PotsdamInclination 87.3

Lifetime July, 2000-September 2010

Nominal Orbit Altitude ~400 km

GRACE Satellite – NASA / DLRInclination 88.9

Lifetime March 2002-present

Nominal Orbit Altitude ~500 km

NADIR 7

Occasions of Common Local Time Passes of CHAMP and GRACE Satellites

Bruinsma, S. L., and J. M. Forbes (2010), Anomalous behavior of the thermosphere during solar minimum observed by CHAMP and GRACE, J. Geophys. Res., 115, A11323, doi:10.1029/2010JA015605.

A0

Quiet Active

CHAMP altitudeAlti

tude

h

1 1( ), ( )T t m t0 0( ), ( )T t m t

aC

qC

1P

2P

1Z

A1

Altitude Response in ThermosphereMass Density to Geomagnetic Activity

0 0

0 11

0 1 0 0 1

( , ) ( , )( , ) exp( , ) ( , ) ( , ) ( ) ( )

h h

h h

T t h m t ht h dh dht h T t h m t h H t H t

3P

GRACE altitude

2Z

B0 B1qG a

G

2 1Z Z

2 1Z Z

2 1

lnZ d PZ Z

NADIR 9

Geomagnetic ActivityDec 2008During a CHAMPand GRACECommon Local Time Orbits

64

66

68

70

F10.7

(a*)

200

400

600

SW (

km/s)

(b*)

0

20

40

n SW (c

m−

3 )

−10−505

10

Bz (

nT)

(c*)

0

2

4Kp

(d*)

12/01 12/03 12/05 12/07 12/09 12/11 12/13−40

−20

0

Dst (

nT)

Quiet Time: December 9-11, 2008<F10.7> = 67<Ap> = 15

Active Time: December 5 – 7, 2008<F10.7> = 68<Ap>= 2

NADIR 10

Thermosphere Mass Density Ratio (Active/Quiet) for Dec 2008 HSS Event: Thermosphere Composition Effect

GRACE Normalized to 476 km

CHAMP Normalized to 332 km

MSIS Density Ratio

MSIS VS. CHAMP and GRACE Observations December 2008

Active time density Quiet time density

NADIR 12

Mg II Correction to F10.7 Index at Solar Minimum

Solomon, S. C., L. Qian, L. V. Didkovsky, R. A. Viereck, and T. N. Woods (2011), Causes of low thermosphericdensity during the 2007–2009 solar minimum, J. Geophys. Res., 116, A00H07, doi:10.1029/2011JA016508.

CHAMP and GRACE Densities with Adjusted F10.7 based on Mg II During the Active Period of the Geomagnetic Storm

During the active time, a good MSIS representation is achieved by lowering f10.7 by 11.

Before After

Original Values

GRACE Densities with MSIS adjusted for F10.7, Ap, and Helium Density

Adjust F10.7 - 14

Adjust F10.7 – 14, Ap+2 Adjust F10.7 – 14, Ap+2, 30% increase in Helium

CHAMP Densities with MSIS adjusted input values of F10.7, Ap, and Helium same as for GRACE

Original Values Adjust F10.7 - 14

Adjust F10.7 – 14, Ap+2 Adjust F10.7 – 14, Ap+2, 30% increase in Helium

Quiet Time Mass Density at GRACE Altitudes is Significantly Impacted by the Presence of Helium

NADIR 17

Mass Density Response as a Function of Altitude in Winter High latitudes is significantly lessened at GRACE Altitudes

by Helium

0 0

exph h

q a qa a

q a q q ah h

T m m mgR dh dhT m k T T

q aa a

q a q q

T m PT m P

NADIR 18

Latitude Dependence in Altitude Response to December 2008 Geomagnetic Activity

Thermosphere Mass Density During CIR/HSS EventsRecurrent geomagnetic activity enabled isolation of CIR/HSS

processes on the preconditioned solar minimum state of the thermosphere.

Response at CHAMP Altitudes: The recurrent geomagnetic activity and constant EUV flux in

2008 enabled a superposed epoch analysis that demonstrated the typical global thermosphere response at 400 km to CIR/HSS events was on average a 75% increase with recovery taking a week or more. Integrated effect rivals CMEs but also demonstrated significant variability

Cont’dResponse at GRACE Altitudes: Significant concentrations of helium exist at GRACE altitudes

(472 km) during quiet geomagnetic activity in the winter hemisphere at solstice in 2008, i.e., the wintertime helium bulge

The mass density response to geomagnetic activity in the contracted winter hemisphere is lessened by the presence of helium leading to strongly varying mass density response with altitude.

F10.7 input to MSIS during December 2008 required a downward adjustment (concomitant with Mg II index) to adequately represent mass density observations and subsequently the modeled drag coefficient requires reevaluation to account for the significant presence of helium.

Need information of composition to adequately describe the thermosphere density response to geomagnetic activity